1. Field of the Invention
This invention relates to a method for the production of macrocyclic lactones which are useful as various synthetic intermediates and particularly important as ingredients of high quality perfumes.
2. Description of the Related Art
Most of macrocyclic lactones are important as fregrance raw materials having musky scent, and a large number of their production methods which use hydroxycarboxylic acid esters as the starting material have been reported. In the case of cyclopentadecanolide for example, British Patent 490,044 discloses a method in which a macrocyclic lactone is produced by intramolecular esterification from an ester of an oxycarboxylic acid with a high boiling point alcohol. According to this method, though it is described that a monohydric or polyhydric alcohol can be used as the high boiling point alcohol, only a polyhydric alcohol, glycerol, is shown in Examples. This method has problems such as reduction of yield due to decomposition of glycerol during the production of monoglyceride of 15-hydroxypentadecanoic acid to be used and the lactonization thereof.
Also, JP-B-41-7770 (the term xe2x80x9cJP-Bxe2x80x9d as used herein means an xe2x80x9cexamined Japanese patent publicationxe2x80x9d) discloses a method in which the macrocyclic lactone is obtained by distillation of hydroxycarboxylic acid ester, the alcohol moiety of which has a lower boiling point than that of macrocyclic lactone, the reaction being with adding glycerol or a liquid capable of co-distilling with lactone. In this method, the macrocyclic lactone cannot be obtained in high yield unless the reaction is carried out by continuously supplying a large amount of the liquid which is co-distilled with the macrocyclic lactone.
In addition, JP-A-64-52739 (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d) discloses a method in which cyclopentadecanolide is produced from methyl 15-hydroxypentadecanoate containing dimethyl 1,15-pentadecandioate. But, this method causes sharp reduction of the yield when dimethyl 1,15-pentadecandioate is present in a large amount due to formation of a copolymer by transesterification with methyl 15-hydroxypentadecanoate, which accompanies distillation of methanol. Thus, not only it is necessary to remove the greater part of dimethyl 1,15-pentadecandioate before the intramolecular esterification of methyl 15-hydroxypentadecanoate, but also there is another problem in that the reaction residue becomes a highly viscous or solid substance which cannot be handled easily, due to formation of copolymers of 1,15-pentadecandioic acid, 15-hydroxypentadecanoic acid and 1,15-pentadecanediol after the reaction. Also, since diester of 1,15-pentadecandioic acid contained in the reaction residue becomes substantially unrecoverable as the result, it poses still another problem in that only about 70% of the diester can be recovered before the reaction.
The invention is a method in which a macrocyclic lactone represented by a formula (2) is produced by carrying out intramolecular esterification of a hydroxycarboxylic acid ester represented by a formula (1), and the macrocyclic lactone can be produced with high yield and high productivity by using a specified long chain alkyl ester of hydroxycarboxylic acid as the starting material. 
In the formulae (1) and (2), m is an integer of from 5 to 10, n is an integer wherein m+n becomes from 11 to 16, X represents xe2x80x94CH2xe2x80x94, xe2x80x94CHxe2x95x90CHxe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94 or xe2x80x94NHxe2x80x94, and R represents a hydrocarbon group having from (m+n+2) to 40 carbon atoms or a group represented by xe2x80x94(AO)pR1 wherein AO represents an alkyleneoxy group having from 2 to 4 carbon atoms, p is average addition mole number of alkylene oxide and R1 represents a hydrocarbon group having a specified number of carbon atoms so that the total number of carbon atoms of the xe2x80x94(AO)pR1 group becomes from (m+n+2) to 40.
Also, the invention is a method for the production of the macrocyclic lactone of formula (2), which comprises intramolecular esterification of a hydroxycarboxylic acid or a lower alkyl (1 to 5 carbon atoms) ester thereof, obtained by partially reducing a dibasic acid represented by a formula (6) or a lower alkyl (1 to 5 carbon atoms) ester thereof, in the presence of an alcohol represented by a formula (5). 
wherein X, m and n are as defined in the foregoing.
HOxe2x80x94Rxe2x80x83xe2x80x83(5)
wherein R is as defined in the foregoing.
According to the invention, R of the ester represented by the general formula (1) has carbon atoms of from 13 to 40 in total, and its examples include straight chain alkyl groups such as eicosyl group and octadecyl group, branched-chain alkyl groups including methyl-branched type branched-chain alkyl groups such as 3,7,11,15-tetramethyl-2-hexadecenyl group and 1-methylpentadecyl group and Guerbet alkyl type branched-chain alkyl groups such as 2-decyltetradecyl group, 2-octyldodecyl group and 2-(1,3,3-trimethylbutyl)-5,7,7-trimethyloctyl group, and polyoxyalkylene alkyl groups having an oxyalkylene addition mole number of from 1 to 12, an oxyalkylene carbon number of from 2 to 4 and an alkyl carbon number of from 1 to 16, such as xe2x80x94(CH2CH2O)6C12H25 and xe2x80x94(CH2CH2O)5{CH2CH(CH3)O}5C12H25.
Among these groups, a branched-chain alkyl group or a polyoxyalkylene alkyl group represented by xe2x80x94(AO)pR1 (wherein AO, p and R1 are as defined in the foregoing) is preferable from the viewpoint of good reaction yield and easy handling due to low melting point, more preferred is a Guerbet alkyl type branched-chain alkyl group or a polyoxyethylene alkyl group having an alkyl carbon number of from 1 to 16 and an ethylene oxide addition mole number of from 1 to 10, and particularly preferred is a Guerbet alkyl type branched-chain alkyl group.
Also, the invention can be carried out within the R carbon number of from (m+n+2) to 40, but since the alcohol formed at the time of intramolecular cyclization reaction has sufficiently higher boiling point than that of the macrocyclic lactone and can therefore be easily separated when the R carbon number is m+n+5 or more, the total carbon number of R is preferably from (m+n+5) to 40, more preferably from (m+n+5) to 36, most preferably from (m+n+5) to 32, from the viewpoint of productivity.
The ester of formula (1) to be used in the invention can be obtained for example by the following methods 1 to 3.
(Method 1) One mole of a hydroxycarboxylic acid represented by a general formula (4) 
(wherein m, n and X are as defined in the foregoing) or a lower alkyl ester thereof and from 1 to 10 moles, preferably from 1 to 3 mole, of an alcohol represented by the formula (5)
HOxe2x80x94Rxe2x80x83xe2x80x83(5)
(wherein R is as defined in the foregoing) are heated at a temperature of from 30 to 300xc2x0 C., preferably from 50 to 250xc2x0 C., under ambient pressure to 1 kPa in the presence or absence of a catalyst, while removing the by-produced water or lower alcohol.
(Method 2) A dibasic diester represented by a formula (3) 
(wherein R, m, n and X are as defined in the foregoing) is partially reduced in the presence of a hydrogenation catalyst, preferably a copper-based hydrogenation catalyst, more preferably a Cuxe2x80x94Cr catalyst, in an amount of from 0.1 to 20% by weight, preferably from 0.2 to 10% by weight, based on the diester, under a hydrogen pressure of from 1 to 40 MPa, preferably from 5 to 30 MPa, and at a temperature of from 100 to 350xc2x0 C., preferably from 150 to 300xc2x0 C.
In this case, the partial reduction is carried out under the condition to suppress the formation of diol by the reduction of both ester groups of the diester as much as possible. It is an effective method to suppress the conversion to keep high selectivity, because selectivity to hydroxycarboxylic acid ester is generally reduced when conversion of diester is increased. This tendency can be found in any of known reactions such as hydrogenation and hydride reduction by a metal hydride or borane. For example, when the reduction is carried out in the presence of a Cuxe2x80x94Cr catalyst until conversion of the diester reaches 60% or more, 25 mole % or more of the diol is formed and yield of the hydroxycarboxylic acid ester of interest therefore is reduced. Accordingly, it is desirable to carry out the reduction by controlling the conversion of diester to 60% or less, and particularly desirable conversion of the diester is from 10 to 45%.
(Method 3) A hydroxycarboxylic acid or a lower alkyl (1 to 5 carbon atoms) ester thereof, which is obtained by partially reducing a dibasic acid represented by the general formula (6) 
(wherein m, n and X are as defined in the foregoing) or a lower alkyl (1 to 5 carbon atoms) ester thereof in the same manner as the case of xe2x80x9cMethod 2xe2x80x9d, and an alcohol represented by the formula (5) are heated with removing the producing water or lower alcohol at a temperature of from 100 to 300xc2x0 C., preferably from 150 to 250xc2x0 C., under ambient pressure to 1 kPa in the presence or absence of a catalyst.
Using the thus obtained hydroxycarboxylic acid ester represented by the formula (1), its intramolecular esterification is carried out to produce the macrocyclic lactone. Among the hydroxycarboxylic acid ester production methods, the partial reduction method of the Methods 2 and 3 is particularly useful when X in the formulae (3) and (6) is xe2x80x94CH2xe2x80x94, because the dibasic acid diester or dibasic acid is industrially available. It is possible to use an un-purified hydroxycarboxylic acid ester mixture containing a dibasic acid diester directly as the starting material, and such a case is desirable because the macrocyclic lactone can be produced efficiently with high yield and high productivity by a simple process without a special purification step.
In addition, since conditions of the esterification and transesterification of the Methods 1 and 3 are similar to those of the intramolecular esterification reaction for obtaining the macrocyclic lactone, it is possible to carry out the intramolecular esterification reaction without separating these two reactions in the reaction system by carrying out the esterification or transesterification in the presence of a catalyst. That is, the macrocyclic lactone of interest can be obtained by distillation when heating the reaction system is continued under a reduced pressure after the removal of water or lower alcohol in the Method 1 or 3.
A method in which the esterification or transesterification represented in the Method 1 or 3 and subsequent intramolecular esterification are carried out simultaneously in parallel is also an embodiment of the invention. That is, a method in which a macrocyclic lactone represented by the formula (2) is produced by the reaction of a hydroxycarboxylic acid or a lower alkyl (1 to 5 carbon atoms) ester thereof, which is obtained by partially reducing a dibasic acid represented by the formula (6) or a lower alkyl ester thereof, in the presence of an alcohol represented by the formula (5). In this case, from the viewpoint of yield and productivity, amount of the alcohol to be present is preferably from 0.01 to 20, more preferably from 0.1 to 10, further preferably from 0.3 to 8, most preferably from 0.5 to 5, as the [alcohol represented by the formula (5)]/[carboxyl group and/or ester group in the reaction mixture] molar ratio.
In this method, the residue after intramolecular esterification of a hydroxycarboxylic acid ester represented by the formula (1) is a low viscosity liquid or low melting point solid which can be handled easily. Also, since a dibasic acid diester, which is desired to recover and reuse, is present in this residue as a low molecular weight monomer or oligomer, it can be recovered easily in a high yield and it can be recycled directly to the reduction. Alternatively, it is possible to recover and recycle the diester as a dicarboxylic acid or a lower alkyl diester thereof by its hydrolysis or alcoholysis with lower alcohol. From the viewpoint of yield and productivity, amount of the dibasic acid diester to be contained in the un-purified hydroxycarboxylic acid ester of formula (1) is preferably 20 or less, more preferably 10 or less, most preferably 6 or less, as a molar ratio of [dibasic acid diester represented by the formula (3)]/[hydroxycarboxylic acid ester represented by the formula (1)].
In the Method 2 or 3, there is a case in which a diol formed by reduction of both of the two ester groups of diester is present. The invention can use either a hydroxycarboxylic acid ester contained mixture from which this diol is removed or a mixture containing the diol for the intramolecular esterification. Also, there is a case in which a monoester is contained in the diester, but it may be used as such. In addition, a mixture containing a polymer of hydroxycarboxylic acid esters represented by the formula (1) or of a hydroxycarboxylic acid ester with a diester or diol can also be used as such.
According to the invention, an alcohol represented by the formula (5) may be coexistent with in the hydroxycarboxylic acid ester of formula (1). Though the reaction can be carried out after removing the alcohol, it is desirable to use a mixture containing the alcohol from both yield and productivity points of view. The alcohol represented by the formula (5) may also be added in the reaction mixture. From the viewpoint of yield and productivity, preferred amount of the alcohol to be present in the reaction system is from 0.01 to 10, more preferably from 0.01 to 5, most preferably from 0.05 to 3, as a molar ratio of [alcohol represented by the formula (5)]/[hydroxycarboxylic acid ester represented by the formula (1)].
Also, when the hydroxycarboxylic acid ester of formula (1) contains a dibasic acid diester, preferred amount of the alcohol of formula (5) to be present is from 0.01 to 20, more preferably from 0.1 to 10, most preferably from 0.3 to 8, particularly preferably from 0.5 to 5, as a molar ratio of [alcohol represented by the formula (5)]/[ester group in the reaction mixture], from the viewpoint of yield and productivity.
According to the invention, the reaction can be carried out in the presence of a catalyst known as an esterification or transesterification catalyst. Preferred examples of such a type of catalyst include metal oxide catalysts such as magnesium oxide, lead oxide, zirconium oxide and zeolite, metal alkoxides such as titanium tetrabutoxide, aluminum triisopropoxide and sodium methoxide, metal hydroxides such as magnesium hydroxide, calcium hydroxide, sodium hydroxide and potassium hydroxide, metal carbonates and fatty acid metal salts such as magnesium carbonate, sodium carbonate, potassium carbonate, potassium acetate, calcium laurate and sodium stearate, and neutral or alkaline catalysts such as magnesium chloride, of which catalysts containing metals of the group II, III or IV, such as magnesium oxide and titanium tetrabutoxide, are more preferred from the viewpoint of reaction yield. Amount of the catalyst to be used can be optionally selected within the range of from 0.01 to 50% by weight based on the hydroxycarboxylic acid ester of formula (1), but is preferably from 0.1 to 20% by weight, more preferably from 0.3 to 10% by weight.
The reaction of the invention can be carried out by charging a transesterification catalyst and the hydroxycarboxylic acid ester of formula (1) at the same time and heating them at a temperature of from 100 to 350xc2x0 C. under a pressure of 13 kPa or less, preferably 2.7 kPa or less, while obtaining the formed macrocyclic lactone by distillation, and the temperature range is preferably from 120 to 300xc2x0 C., more preferably from 150 to 270xc2x0 C., most preferably from 180 to 270xc2x0 C., from the viewpoint of yield and productivity.
According to the method of the invention, like the case of the use of a glycerol ester as the xcfx89-hydroxycarboxylic acid ester, a macrocyclic lactone can be produced with a high productivity without causing problems such as reduction of the yield by decomposition of glycerol. Also, when a hydroxycarboxylic acid ester mixture obtained by partial reduction of a diester is used, the macrocyclic lactone of interest can be produced easily and with a high yield without removing the diester from the reaction mixture prior to the intramolecular esterification reaction of hydroxycarboxylic acid ester. In addition, the unreacted diester can be recovered from the reaction residue easily with a high yield. The thus obtained macrocyclic lactone contains almost no lactone dimer and is almost free from coloration.